Absorption refrigeration cycles using a lgwp refrigerant

ABSTRACT

An absorptive refrigeration method and refrigerant/absorbant pairs comprising fluorinated organic compounds, such as fluorinated organic compounds having from one to eight carbon atoms (C1-C8), including hydrofluoroolefin and/or hydrochlorofluoroolefin compounds. In certain embodiments, a fluorinated organic compound, including certain hydrofluoroolefin and/or hydrochlorofluoroolefin compounds (e.g. C2-C4 hydrofluoroolefin and/or hydrochlorofluoroolefin compounds) is/are utilized as the refrigerant, with the absorbant portion either being a fluorinated organic compound or a non-fluorinated oil.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to and claims the priority benefit of U.S.provisional application Ser. No. 61/320,305, filed Apr. 1, 2010, thecontents of which are incorporated herein by reference.

The application is also a continuation-in-part of U.S. application Ser.No. 12/432,466, filed Apr. 29, 2009, which claims priority to UnitedStates provisional application serial number 61/049,069, filed Apr. 30,2008, the contents each of which are incorporated herein by reference.

FIELD OF THE INVENTION

This invention relates to economical absorption refrigeration systemsthat employ refrigerants with low global warming potential (GWP) and lowozone depletion potential (ODP).

BACKGROUND OF THE INVENTION

Absorption refrigeration is a more economical alternative to compressionrefrigeration when a source of waste or other low-cost heat (e.g. solarheating) is available. As such, absorption refrigeration has thepotential to play a very important role in reducing the environmentalimpact of cooling systems that operate in hot environments.

Both absorption refrigerators and vapor compression refrigerators use arefrigerant with a very low boiling point. In both types, when thisrefrigerant evaporates or boils, it takes some heat away with it,providing the cooling effect. However, absorption refrigeration andvapor compression refrigeration differ in the way the refrigerant ischanged from a gas back into a liquid so that the cycle can repeat. Avapor compression refrigerator uses mechanical work, frequently suppliedby an electrically-powered compressor, to increase the pressure on thegas, and then condenses the hot, high pressure gas back to a liquid byheat exchange with a cool fluid (usually air). An absorptionrefrigerator does not use mechanical work to increase the pressure ofthe pressure of the gas and changes the gas back into a liquid using adifferent method that needs only a low-power pump, or optionally onlyheat, thereby providing a system that has fewer moving parts, whichincreases the overall lifetime of the system.

Residential and commercial buildings are large consumers of energy andthe major consumer of electricity with demand varying constantly. Duringlow to moderate demand periods electricity is produced by the mostefficient equipment utilizing nuclear, coal, or hydroelectric energysources since this equipment is run nearly continuously. However duringpeak demand, less costly and less efficient equipment is used typicallyrunning on natural gas or fuel oil which raises concerns about fuelsecurity in the case of oil use and price stability for natural gas.Peak demand also set the overall size of the electrical system thatincludes the generating and distribution systems. In addition, reducingdemand at times when the generating or transmission systems are at theirlimit is an effective way to improve reliability of electricity supplyand avoid interruptions that can have significant negative economicimpact.

Solar energy can be utilized through the use of relatively inexpensivecollector panels with the solar energy transferred to a working fluidwhich is typically water with glycols added to suppress the freezingpoint. This fluid then becomes the heat source that powers theabsorption cooling system. In addition, when cooling is not required,this can be used to heat potable water. An additional benefit for newinstallations is that the base vapor compression cooling system can bedownsized and thereby operate with less cycling that will improve theperformance of this system. Also, absorption refrigeration can have anadvantage is such environments because it holds the potential to use thesame source of energy that typically increases the load on thesesystems, i.e. solar energy, to provide needed cooling.

Common examples of refrigeration cycles are food refrigerators andfreezers and air conditioners. The reversible-cycle heat pumps forproviding thermal comfort also work by exploiting the physicalproperties of evaporating and condensing a refrigerant. In heating,ventilation, and cooling (HVAC) applications, a heat pump normallyrefers to a refrigeration device that includes a reversing valve andoptimized heat exchangers so that the direction of heat flow may bereversed. Most commonly, during the heating cycle, heat pumps draw heatfrom the air or from the ground, or even from water.

Although absorption systems have been in limited use for many years,applicants have come to recognize that conventional working fluids havehad significant disadvantages that have limited their success. Forexample, the two most common absorption refrigeration pairs areNH₃-water and water-LiBr. NH₃-water use NH₃ as the refrigerant and wateras the absorbent. Although NH₃ performs well as a refrigerant in manyapplications, the toxicity of NH₃ limits it use in areas that can beoccupied by the public. In addition, compatibility issues with one ofthe more common materials of construction in cooling systems, copper,can increase the cost of the installed systems based on NH₃-water byhaving to use less desirable and/or more expensive materials. Withrespect to water-LiBr, a problem arises because water is not a suitablerefrigerant in many important cases of interest. Applicants have come toappreciate that water has two main drawbacks that limit its viability incertain important applications. The first is that due to the lowpressures the equipment sizing becomes impractical for manyapplications. Second due to the freezing point of water it cannot beused at temperatures below 0° C. As a result, due to issues such astoxicity and/or flammability and/or corrosiveness and/or equipment cost,such systems are typically only used in industrial settings or toapplications were only a very small charge of refrigerant is required(low capacity systems, ie some refrigerators in hotels and RVs, althougheven these have largely disappeared due to the toxicity of NH₃).

Accordingly, applicants have come to recognize a continuing need forsafer and environmentally friendly refrigerant for absorption-typerefrigeration systems. Applicants have also come to recognize apotential advantage to be gained by systems that can provide effectiveand environmentally acceptable fluids for use in a variety ofapplications from industrial heat recovery to residential solar assistedrefrigeration.

SUMMARY OF THE INVENTION

Applicants have found that certain refrigerant/absorbant pairscomprising fluorinated organic compounds, including fluorinated organiccompounds having from one to eight carbon atoms (C1-C8), and, in certainembodiments, certain hydrofluoroolefin and/or hydrochlorofluoroolefincompounds, are well suited for use as and have particular advantage inabsorption refrigeration. In certain embodiments, a fluorinated organiccompound in accordance with the present invention, particularly, thoughnot exclusively, certain hydrofluoroolefin and/orhydrochlorofluoroolefin compounds, and/or C2-C4 hydrofluoroolefin and/orhydrochlorofluoroolefin compounds is/are utilized as the refrigerant,with the absorbant portion either being fluorinated organic compoundand/or a non-fluorinated oil. Hydrofluoroolefins, such as, but notlimited to, HFO-1234yf (e.g. 1,1,1,2-tetrafluoropropene) andHFO-1234ze(E) (e.g. 1,1,1,3-tetrafluoropropene), have been found to haveexcellent refrigeration capabilities and a very short atmosphericlifetime which makes them environmentally benign and are preferred foruse, preferably as refrigerant, in accordance with the presentinvention. Hydrochlorofluoroolefins, particularlymonofluorotrifluopropenes such as, but not limited to, HCFO-1233zd(1-chloro-3,3,3-trifluoropropene) have also been found to have excellentrefrigeration capabilities and a very short atmospheric lifetime whichmakes them environmentally benign and are preferred for use, preferablyas absorbent, in accordance with the present invention. Theserefrigerants also have the added benefit of being compatible with copperand aluminum. The use of copper and aluminum both increases theefficiency due to improved heat transfer and decreases the overall cost.

In certain embodiments, the absorption refrigeration fluids of thepresent invention comprises a first fluorinated organic compound whichacts as an absorbent and has a relatively high boiling point and asecond fluorinated organic compound which acts as a refrigerant and hasa relatively low boiling point. In certain instances, the absorbent,which comprises the first fluorinated organic compound, has a boilingpoint that is at least 40° C. higher than the boiling point of thesolute which comprises the second fluorinated organic compound. Infurther embodiments, the absorbent compound is a non-ionic compound andalso has an aggregate number of carbon/oxygen atoms that is at least two(2) greater than the aggregate number of carbon/oxygen atoms in therefrigerant. Thus, in embodiments in which the refrigerant comprises oneor more C1-C4 fluorinated compounds, or one or more C2-C4hydrofluoroolefin and/or hydrochlorofluoroolefin compounds, theabsorbant compounds comprise one or more C2-C8 fluorinated compounds,and in certain embodiments one or more C3-C8 hydrofluoroolefin and/orhydrochlorofluoroolefin compounds.

According to certain aspects of such embodiments, the absorbant portionof the fluid is selected from the group consisting of fluoroethers,fluoroketones, HFCs, HFOs (including HFCOs), and combinations of these,and the refrigerant portion of the pair is selected from the groupconsisting of HFCs, HFOs (including HFCOs), CO₂ and combinations ofthese. A non-limiting example of a fluoroether for use as an absorbentin accordance with the present invention is methyl nonafluorobutylether. A nonlimiting example of fluoroketone for use as a absorbent inaccordance with the present invention isperfluoro(2-methyl-3-pentanone). A nonlimiting example of an HFC for useas an absorbent in accordance with the present invention is HFC-245fa(e.g. 1,1,1,3,3-pentafluoropropane). A nonlimiting example of an HFO foruse as a absorbent solvent in accordance with the present invention isHFO-1233zd, including HFO-1233zd(E). A nonlimiting example of an HFO foruse as a refrigerant in accordance with the present invention isHFO-1234yf. A nonlimiting example of an HFC for use as a refrigerant inaccordance with the present invention is HFC-32 (difluoromethane).Particularly preferred, though not exclusive, in accordance with thepresent invention are the refrigerant/absorbent pairs HFC32/HFC-245fa,HFC-32/HFC-1234yf, HFC-32/1233zd(E) and HFO-1234yf/1233zd(E), and mostpreferably, though not exclusively, the use of such pairs in connectionwith absorption refrigeration systems which comprise energy input in theform of solar power, and even more preferably, though not exclusively,the use of such solar power energy input to decrease the peak demand ofa commercial system.

In certain other embodiments, the refrigerant portion of the pair inaccordance with the present invention is selected from among certainhydrofluoroolefin and/or hydrochlorofluoroolefin compounds and theabsorbent and/or solvent portion is or includes a nonfluoroinated oil,which may selected from organic oils, such as polyalkyene glycol oil,poly alpha olefin oil, mineral oil, and polyol ester oil, includingcombinations of these. It has been discovered that solutions of theserefrigerants and oils enable the refrigerant to be used as a workingfluid in an absorption-type refrigeration system. Many of theserefrigerants are characterized as having a low-GWP (i.e., <1000, or <100relative to CO₂), a low or no appreciable ozone depletion potential, andare non-toxic and non-flammable. One of skill in the art will appreciatethat, in one aspect, the present invention includes a combination of therefrigerants, fluorinated absorbents and non-fluorinated oils.

Accordingly, an aspect of this invention involves a method for providingrefrigeration comprising: (a) evaporating a first liquid-phaserefrigerant stream comprising one or more fluorinated organic compoundshaving from one to eight carbon atoms, to produce a low-pressurevapor-phase refrigerant stream, wherein said evaporating transfers heatfrom a system to be cooled; (b) contacting said low-pressure vapor-phaserefrigerant stream with a first liquid-phase solvent stream comprisingone or more organic compounds having an aggregate number ofcarbon/oxygen atoms that is at least two (2) greater than an aggregatenumber of carbon/oxygen atoms in the refrigerant under conditionseffective to dissolve substantially all of the refrigerant of thevapor-phase refrigerant stream into the solvent of the firstliquid-phase solvent stream to produce a refrigerant-solvent solutionstream; (c) increasing the pressure and temperature of therefrigerant-solvent solution stream; (d) thermodynamically separatingsaid refrigerant-solvent solution stream into a high-pressurevapor-phase refrigerant stream and a second liquid-phase solvent stream;(e) recycling said second liquid-phase solvent stream to step (b) toproduce said first liquid-phase solvent stream; (f) condensing saidhigh-pressure vapor-phase refrigerant stream to produce a second liquidphase refrigerant stream; and (g) recycling said second liquid-phaserefrigerant stream to step (a) to produce said first liquid-phaserefrigerant stream.

As used herein, the terms “low-pressure vapor-phase refrigerant” and“high-pressure vapor-phase refrigerant” are relative to one another.That is, a low-pressure vapor-phase refrigerant has a pressure above 0psia, but lower than thepressure of the high-pressure vapor-phaserefrigerant. Likewise, the high-pressure vapor-phase refrigerant has apressure below the composition's critical point, but higher than thepressure of the low-pressure vapor-phase refrigerant.

As used herein, the term “substantially all” with respect to acomposition means at least about 90 weight percent based upon the totalweight of the composition.

In another aspect, the invention provides an absorption refrigerationsystem comprising: (a) a refrigerant selected from the group consistingof one or more fluorinated organic compounds; (b) an absorbentcomprising one or more fluorinated organic compounds having from one toeight carbon atoms (C1-C8) having a boiling point that is at least 40°C. higher than the boiling point of the refrigerant; (c) an evaporatorsuitable for evaporating said refrigerant; (d) a mixer suitable formixing said refrigerant with said absorbent, wherein said mixer isfluidly connected to said evaporator; (e) an absorber suitable fordissolving at least a portion of said refrigerant into said absorbent toproduce a solution, wherein said absorber is fluidly connect to saidmixer; (f) a pump fluidly connected to said absorber; (g) a heatexchanger fluidly connected to said pump; (h) a separator suitable forthermodynamically separating said solution into a vapor refrigerantcomponent and a liquid absorbent component, wherein said separator isfluidly connected to said heat exchanger; (i) an oil return line fluidlyconnected to said separator and said mixer, and (j) a condenser suitablefor condensing said vapor refrigerant component, wherein said condenseris fluidly connected to said separator and said evaporator.

This invention is an environmentally friendly, economical refrigerationprocess.

In certain embodiments, the present methods and systems are powered, atleast in part, by solar energy to provide cooling at times of greatestload. The absorption refrigerants are low global warming, safe to use,and energy efficient

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graphic representation of data showing the solubility ofHFC-1234ze(E) in a PAG lubricant;

FIG. 2 is a schematic view of an absorption refrigeration cycleaccording to one embodiment of the invention;

FIG. 3 is a schematic view of another absorption refrigeration cycleaccording to another embodiment of the invention;

FIG. 4 is a schematic view of one embodiment of an absorptioncompression system (B) and a vapor compression system (A);

FIG. 5 is a graphic representation of data showing GWP impact on LifeCycle Climate Performance (LCCP); and

FIG. 6 is a graphic representation of data showing GWP impact on LCCP,including impact of reduced efficiency.

DETAILED DESCRIPTION OF THE INVENTION

Absorption systems and vapor compression systems both operate via Carnotidealized energy conversion cycles moving heat energy from a lowtemperature reservoir (the cooling load) to a high temperature reservoir(the ambient) by the use of thermal energy, Qin, for absorptiontechnology or shaft work, Wsh, or mechanical vapor compression. Theillustration of FIG. 4 provides a simplified schematic of generalizedversions of each of such systems. As can be seen by these figures, bothabsorption and vapor compression systems utilize a condenser to exchangeheat with the ambient, an expansion device, and an evaporator to performthe cooling of the system. The primary difference is that absorptionsystems utilize thermal energy to serve as a “thermal” or “chemical”compressor through the use of the chemical potentials between therefrigerant and the absorbent while a vapor compression system utilizesmechanical compressors drawing shaft power that is frequently electric.Applicants have found an efficient absorption system by identifyingsuitable refrigerant-absorbent pairs that efficiently perform thecompression of the refrigerant. In many embodiments, the only movingpart in an absorption system is the pump which provides a long lifetimeof the overall system.

In certain embodiments of the invention, certain refrigerant/absorbantpairs comprising fluorinated organic compounds, including fluorinatedorganic compounds having from one to eight carbon atoms (C1-C8), and, incertain embodiments, certain hydrofluoroolefin and/orhydrochlorofluoroolefin compounds, are well suited for use as and haveparticular advantage in absorption refrigeration. In certainembodiments, a fluorinated organic compound in accordance with thepresent invention, particularly, though not exclusively, certainhydrofluoroolefin and/or hydrochlorofluoroolefin compounds, and/or C2-C4hydrofluoroolefin and/or hydrochlorofluoroolefin compounds is/areutilized as the refrigerant, with the absorbant portion either being afluorinated organic compound or a non-fluorinated oil.Hydrofluoroolefins, such as, but not limited to, HFO-1234yf (e.g.1,1,1,2-tetrafluoropropene) and HFO-1234ze(E) (e.g.1,1,1,3-tetrafluoropropene), have been found to have excellentrefrigeration capabilities and a very short atmospheric lifetime whichmakes them environmentally benign and are preferred for use, preferablyas refrigerant, in accordance with the present invention.Hydrochlorofluoroolefins, particularly monofluorotrifluopropenes suchas, but not limited to, HCFO-1233zd (1-chloro-3,3,3-trifluoropropene)have also been found to have excellent refrigeration capabilities and avery short atmospheric lifetime which makes them environmentally benignand are preferred for use, preferably as absorbent, in accordance withthe present invention. These refrigerants also have the added benefit ofbeing compatible with copper and aluminum. The use of copper andaluminum both increases the efficiency due to improved heat transfer anddecreases the overall cost.

In certain embodiments, the absorption refrigeration fluids of thepresent invention comprises a first fluorinated organic compound whichacts as an absorbent and has a relatively high boiling point and asecond fluorinated organic compound which acts as a refrigerant and hasa relatively low boiling point. In certain instances, the absorbent,which comprises the first fluorinated organic compound, has a boilingpoint that is at least 40° C. higher than the boiling point of thesolute which comprises the second fluorinated organic compound. Infurther embodiments, the absorbent compound is a non-ionic compound andalso has an aggregate number of carbon/oxygen atoms that is at least two(2) greater than the aggregate number of carbon/oxygen atoms in therefrigerant. Thus, in embodiments in which the refrigerant comprises oneor more C1-C4 fluorinated compounds, or one or more C2-C4hydrofluoroolefin and/or hydrochlorofluoroolefin compounds, theabsorbant compounds comprise one or more C2-C8 fluorinated compounds,and in certain embodiments one or more C3-C8 hydrofluoroolefin and/orhydrochlorofluoroolefin compounds.

According to certain aspects of such embodiments, the absorbant portionof the fluid is selected from the group consisting of fluoroethers,fluoroketones, HFCs, HFOs (including HFCOs), and combinations of these,and the refrigerant portion of the pair is selected from the groupconsisting of HFCs, HFOs (including HFCOs), CO₂ and combinations ofthese. A nonlimiting example of a fluoroether for use as a solvent inaccordance with the present invention is methyl nonafluorobutyl ether. Anonlimiting example of fluoroketone for use as a absorbent in accordancewith the present invention is perfluoro(2-methyl-3-pentanone). Anonlimiting example of an HFC for use as an absorbent in accordance withthe present invention is HFC-245fa (e.g. 1,1,1,3,3-pentafluoropropane).A nonlimiting example of an HFO for use as a absorbent solvent inaccordance with the present invention is HFO-1233zd, includingHFO-1233zd(E). A nonlimiting example of an HFO for use as a refrigerantin accordance with the present invention is HFO-1234yf. A nonlimitingexample of an HFC for use as a refrigerant in accordance with thepresent invention is HFC-32 (difluoromethane). Particularly preferred,though not exclusive, in accordance with the present invention are thepairs HFC32/HFC-245fa, HFC-32/HFO1234yf, HFC-32/1233zd(E) andHFO-1234yf/1233zd(E), and most preferably, though not exclusively, theuse of such pairs in connection with absorption refrigeration systemswhich comprise energy input in the form of solar power, and even morepreferably, though not exclusively, the use of such solar power energyinput to decrease the peak demand of a commercial system.

Refrigerants for this invention are not limited to the foregoingembodiments and also include hydrofluoroolefins andhydrochlorofluoroolefins of the formula C_(w)H_(x)F_(y)Cl_(z) where w isan integer from 3 to 5, x is an integer from 1 to 3, and z is an integerfrom 0 to 1, and where y=(2·w)−x−z. Certain refrigerants includehydrohalopropenes, including tetrahalopropenes, e.g. tetrafluoropropenesand mono-chloro-trifluoropropenes, or tetrahalopropenes having a —CF₃moiety, e.g. 1,1,1,2-tetrafluoropropene, 1,3,3,3-tertafluoropropene,1-chloro-3,3,3-trifluoropropene, including all stereoisomers thereof,such as trans-1,3,3,3-tertafluoropropene,cis-1,3,3,3-tertafluoropropene, trans-l-chloro-3,3,3-trifluoropropene,cis-l-chloro-3,3,3-trifluoropropene and 3,3,3-trifluoropropene. Certainuseful refrigerants also comprise a mixture of two or morehydrofluoroolefins, hydrochlorofluoroolefins, as well as mixtures ofboth hydrofluoroolefins and hydrochlorofluoroolefins.

In certain embodiments of the invention, a hydrofluoroolefin and/orhydrochlorofluoroolefin refrigerant is used in an absorption-typerefrigeration system as a working fluid, i.e., a fluid that changesstates from gas to liquid or vice versa via a thermodynamic cycle. Thisphase change is facilitated by dissolving the vapor-phase refrigerant inan oil solvent (as an absorbent with an with an additional absorbentprovided herein) to form a solution. Preferably, though not exclusively,a pump and heat exchanger are used to efficiently increase thesolution's pressure and temperature, respectively. The pressurized andheated solution is then flashed to produce a refrigerant vapor at highpressure. This high pressure vapor is then passed through a condenserand evaporator to transfer heat from a system to be cooled.

Solvents useful in the present invention may be selected from the groupconsisting of polyalkyene glycol oil, a poly alpha olefin oil, a mineraloil and a polyolester oil. The oils selected are generally thermallystable, have very low vapor pressures, and are non-toxic andnon-corrosive. Certain oils that fit these criteria and can be used withvarious olefins above are poly-ethylene glycol oils, polyol ester oils,polypropylene glycol dimethyl ether-based and mineral oil. Such oils, asdiscussed herein, may also act in a absorbent capacity either alone, orin combination with one or more of the fluorinated absorbent discussedherein. To this end, the discussion herein with respect to the mixing ofrefrigerant and solvent is equally applicable to solutions including therefrigerant, fluorinated absorbent and solvent.

In certain embodiments, the refrigerant and solvent are mixed inproportions and under conditions effective to form a solution in whichthe refrigerant is dissolved in the solvent. Preferably, though notexclusively, the mixture of refrigerant and solvent is in proportions inwhich a substantial portion, or substantially all, of the refrigerantmixed with the solvent is dissolved in the solvent. That is, in certainembodiments, the amount of refrigerant to be mixed with the solvent isbelow the saturation point of the solvent at the operating temperatureand pressure of the refrigerant system. Maintaining the refrigerantconcentration below the saturation point decreases the likelihood thatvapor refrigerant will reach the pump, where it could lead tocavitations.

The refrigerant and solvent may be mixed by a mixer. Such mixersinclude, but are not limited to, static mixers and aspirators (i.e.,venturi pump). In certain embodiments, the mixer is a simple junction oftwo transfer lines (e.g., pipes, tubes, hoses, and the like) thatproduces a turbulent flow, such as a T-fitting.

Dissolution of the low-pressure vapor phase refrigerant in the oilsolvent may occur at refrigerant temperature of about −10° C. to about30° C., or about 0° C. to about 10° C.

The dissolution of the refrigerant in the solvent may occur, at least toa major portion, in an absorber. The absorber can be of any type that issuitable for dissolving a refrigerant gas into an oil-based solvent.Examples of absorbers include heat exchangers through or around which acooling medium is circulated.

The solution comprising the refrigerant and solvent is pumped against ameans of resistance to increase the pressure of the solution. Pumpingthe liquid solution to a high operating pressure typically requiressignificantly less energy compared to compressing a vapor refrigerantusing a compressor. In addition to expending less energy, pumps aretypically less costly to install and maintain compared to compressors.This energy and cost savings is a distinct advantage of the presentinvention over conventional compression-type refrigeration systems.

The solution is also heated, in certain embodiments, after beingpressurized. Heating may be accomplished using a heat exchanger, such asshell-and-tube heat exchangers and plate heat exchangers or adistillation column. In certain embodiments, heating the solutioninvolves a waste-heat recovery unit (WHRU) (i.e., a heat exchanger thatrecovers heat from a hot gas or liquid stream, such as, but not limitedto, exhaust gas from a gas turbine, heat generated in a solar collectoror waste gas from a power plant or refinery). The WHRU working mediummay include water-either pure or with triethylene glycol (TEG)—thermaloil or other mediums conducive to heat transfer. In other embodiments,heating the solution involves the use of geothermal, solar derived heator direct heating from combustion of a fuel such a propane.

After the solution is heated and pressurized, it is subjected to athermodynamic separation process to produce a vapor refrigerant fractionand a liquid solvent fraction. Examples of such thermodynamic separationprocesses include column distillation and flashing. Since the twofractions are in different phases, they can be separated easily.

In certain embodiments, the liquid solvent phase is recirculated back tothe mixer, while the vapor phase comprising the refrigerant istransferred to a condenser where at least a portion, or substantiallyall, of the refrigerant is converted from its vapor phase to a liquidphase.

The types of condenser useful in the invention are not particularlylimited provided that they are suitable for condensing ahydrofluoroolefin or hydrochlorofluoroolefin refrigerant. Examples ofcondensers include horizontal or vertical in-shell condensers andhorizontal or vertical in-tube condensers.

The liquid phase refrigerant is passed through an expansion valve tolower the pressure of the refrigerant and, correspondingly, cool therefrigerant. The cooled, throttled refrigerant can be in a liquid-phase,vapor-phase, or a mixed-phase.

The refrigerant is then passed through an evaporator wherein the coolingcapacity of the refrigerant during evaporation is used to extract heat(i.e., refrigerate) the system to be cooled. Preferably, though notexclusively, the material to be cooled in the system is water, with orwithout a heat transfer additive such as PEG, which can be used, forexample, as chilled water circulated to air handlers in a distributionsystem for air conditioning. However, the material to be cooled can alsobe air used directly for air conditioning. In addition, the externalmaterial can also be any flowable material that needs to be cooled, andif water or air, the cooled materials can be used for purposes otherthan air conditioning (e.g., chilling food or other products).

The type of evaporator used to evaporate the liquid-phase refrigerant isnot particularly limited provided that it is suitable for evaporating ahydrofluoroolefin or hydrochlorofluoroolefin refrigerant. Examples ofuseful evaporators include forced circulation evaporators, naturalcirculation evaporator, long-tube and short-tube vertical evaporators,falling film evaporators, horizontal tube evaporators, and plateevaporators.

After the refrigerant is evaporated, it becomes a low-pressurevapor-phase refrigerant typically, though not exclusively, having atemperature of about 30° C. to about 60° C., in certain embodimentsabout 40° C. to about 50° C. The low-pressure vapor-phase refrigerant isrecirculated back to the mixer.

The processes of the present invention are, in certain embodiments,closed-loop systems wherein both the refrigerant and solvent arerecirculated. Absorption refrigeration systems according to thisinvention involve a single, double, or triple effect absorptionrefrigeration process. Single and double effect processes are describedin the Examples and figures described below.

Consideration of non-ideal behavior properties such as viscous friction(pressure drops), thermal mixing (exergy exchange), mass mixing (rate ofabsorption and desorption), heat transfer effects and basic control ofthe system can play an important role in the selection of therefrigerant and other system parameters. In addition, working pairsolubilities and thermophysical properties could be determined andconsidered in connection with determining the mixture parameters andoperating parameters. The mixing (thermal and mass) of the working fluidpairs can also be important to the design of the absorber, whichfrequently is the most engineering complex component. The rate ofabsorption can also be important to determine and evaluate for differentrefrigerant flow configurations, and consideration of transient systemstartup effects may be necessary. Furthermore, consideration of theenvironmental effects on refrigeration systems may involve evaluation ofdirect contribution due to fluid leakage (direct effect fluid GWP), theamount of energy it consumes (indirect effect), the amount of energyused to produce the device (indirect), and the amount of energy used todecommission the device (indirect). By limiting only to technologiesthat have a low direct effect does not correctly solve the overallproblem of energy usage and impact to our environments. As explainedbelow, LCCP analysis can be used to evaluate the choices in technologydevelopment. Not only should working fluids have a low overall fluidGWP, they must also have a good societal payback through reduced energyconsumption toward energy independence and technology development. Inorder to determine the environmental impact of the choice ofrefrigerants for this application, an analysis of both the direct andindirect contributions to global warming were conducted. The directcontributions come from refrigerant emissions and the indirectcontributions are due to the burning of fossil fuels to supply the powerconsumed by the equipment.

To determine the power consumption of a typical heat pump over thecourse of a year, a bin analysis was performed using averaged weatherdata for an average of 29 cities across the U.S. Data from an AirConditioning, Heating and Refrigeration Institute Standard for chillers(AHRI Std 550) was used for average U.S. weather. Assumptions for thisanalysis included a value of 0.65 kg of CO2 per kW-hr of electricalproduction for the U.S., a 5% annual leakage rate and a 15% end-of-lifeloss, and a 15-year life. The impacts were determined by:

Direct=Refrigerant Charge×(Annual loss rate×Lifetime +End-of-lifeloss)×GWP

Indirect=Annual Power Consumption×Lifetime×0.65

Using this information a Life Cycle Climate Performance (LCCP) analysiswas performed and is shown in FIGS. 5 and 6 herein. It is very clearfrom these results that the indirect contributors dominate anycontributions from refrigerant emissions. Any reduction below the 400level has no significant impact on the total.

The following examples are given as specific illustrations of theinvention. It should be noted, however, that the invention is notlimited to the specific details set forth in the examples.

EXAMPLES Example 1

The solubility of trans-1,3,3,3-tertafluoropropene (1234ze(E)) in FordMotor craft oil (a PAG refrigerant compressor oil meeting Fordspecification No. WSH-M1C231-B) was measured by means of amicro-balance. The solubility that was measured along with thecorrelation of the data using the Non-Random Two Liquid (“NRTL”)activity coefficient model (Renon H., Prausnitz J. M., “LocalCompositions in Thermodynamic Excess Functions for Liquid Mixtures,”AlChE J., 14(1), S.135-144, 1968)) is shown in FIG. 1. From these datait is seen that the Ford Motor Craft oil has nearly negligible vaporpressure and that the NRTL model can accurately represent the data.

Example 2

The data from examples 1 was used to develop a single effect absorptioncycle. A representative schematic of a single effect absorption systemof this invention is illustrated in FIG. 2.

In FIG. 2, a Ford Motorcraft polypropylene glycol dimethyl ether-basedoil from line 10 is mixed with a liquid 1234ze(Z) refrigerant from line4 in a closed mixer 20 (which can be a simple “T” joint connecting lines4 and 10 to line 5). The mixture in passed though line 5 to an absorber22 where the gaseous 1234ze(Z) dissolves into the oil. The liquidmixture is passed though line 6 to pump 24 that pressurizes the mixtureand passes the mixture through line 7 to heat exchanger/boiler 26. Inboiler 26, heat is exchanged with the mixture. The source of that heatcan be waste heat from an industrial operation (e.g., power generation)external to the heat exchanger. The temperature of the mixture is raisedto a temperature where the 1234ze(Z) refrigerant can separate from theoil. The heated mixture is removed through line 8 from the heatexchanger and introduced to a separator 28 whereby the refrigerantseparates substantially in a vapor state from the oil that remainssubstantially in a liquid state. The oil is then returned through line 9and through an oil valve 30 where its pressure is decreased to match thepressure in line 4. From valve 30 the oil is returned via line 10 tomixer 20 where it is again mixed with the refrigerant to repeat theprocess.

From separator 28, the refrigerant vapor is passed through line 1 to acondenser 32 so as to liquefy it. The liquid is passed through line 2through an expansion valve 34, throttling the liquid refrigerant to coolthe refrigerant. The cooled, throttled refrigerant can be liquid, vaporor a combination depending on the operator's choice. The cooledrefrigerant is passed through an evaporator 36 whereby the coolingability of the refrigerant is utilized to cool a material (water or air)that is in a heat-exchanging relationship with evaporator 36. Therefrigerant is then returned from evaporator 36 through line 4 to mixer20 where it is again mixed with the oil to repeat the process again.

The input parameters for the single effect absorption cycle of FIG. 2are:

1) Evaporator 28: 2° C.

2) Condenser 32: 40° C.

3) 3000 kJ/hr supplied to boiler 26

4) Saturated liquid leaving absorber 22

5) Superheat leaving the evaporator 36 through line 4: 3° C.

6) The composition of stream 8 is 90 wt % oil and 10 wt % refrigerant.

With these parameters, the calculated coefficient of performance (“COP”)using 1234ze(Z) and the Ford motor craft oil is 4.56.

Example 3

A representative schematic of a double effect absorption is illustratedin FIG. 3.

In FIG. 3, a Ford Motorcraft polypropylene glycol dimethyl ether-basedoil from line 17 is mixed with a liquid 1234ze(Z) refrigerant from line4 in a closed mixer 40. The mixture is passed though line 5 to a firstabsorber 42 where the gaseous 1234ze(Z) dissolves into the oil. Themixture is passed though line 6 to first pump 44 that pressurizes themixture and passes the mixture through line 7 to first heatexchanger/boiler 46. In boiler 46, heat is exchanged with the mixture.The source of that heat can be waste heat from an industrial operation(e.g., power generation) external to heat exchanger 46. The temperatureof the mixture is raised. The heated mixture is removed through line 8from heat exchanger 46 and introduced to a second mixer 48 where it ismixed with oil from line 15. The mixture from mixer 48 is taken throughline 9 and introduced to second absorber 50 to ensure that all of the1234ze(Z) is dissolved in the oil. From second absorber 50, the mixtureis drawn through line 10 to a second pump 52 that pumps the mixture to asecond boiler 54 where the temperature of the mixture is raised to atemperature where the 1234ze(Z) refrigerant can separate from the oil. Asource of heat to boiler 54 is provided to accomplish this, which sourcecan be of the type described above.

The mixture is taken from second boiler 54 through line 12 to separator56 whereby the refrigerant separates substantially in a vapor state fromthe oil that remains substantially in a liquid state. The oil is thenreturned through line 13 to tee 58 where it is split between line 14 and16. Line 14 sends oil through a second oil valve 60 and through line 15to second mixer 48. Line 16 sends oil through a first oil valve 62 wherethe pressure is decreased to match the pressure in line 4. The oil thenpasses through line 17 to mixer 40 where it is again mixed with therefrigerant to repeat the process.

From separator 56, the refrigerant vapor is passed through line 1 to acondenser 64 so as to liquefy it. The liquid is passed through line 2through an expansion valve 66, throttling the liquid refrigerant to coolthe refrigerant. The cooled, throttled refrigerant can be liquid, vaporor a combination depending on the operator's choice. The cooledrefrigerant is passed through an evaporator 68 whereby the coolingability of the refrigerant is utilized to cool a material (water or air)external of evaporator 68. The refrigerant is then returned fromevaporator 68 through line 4 to mixer 40 where it is again mixed withthe oil to repeat the process again. The input parameters for the doubleeffect absorption cycle of FIG. 3 are:

1) Evaporator 68: 2° C.

2) Condenser 64 40° C.

3) Pressure exiting Pump 44 is exp(1n(√{square root over(P_(evap)·P_(cond))}))

4) 1500 kJ/hr supplied to boiler 46

5) Saturated liquid leaving both Absorber 42 and Absorber 50

6) Superheat leaving the evaporator 68: 3° C.

7) Tee 58 splits the flow 30% to stream 14 and 70% to stream 16.

8) The composition of stream 12 is 90 wt % oil and 10 wt % refrigerant.

With these parameters the calculated COP using 1234ze(Z) and Ford motorcraft oil is 5.04.

One skilled in the art will recognize that there are other variations ofthe absorption refrigeration systems disclosed above that can bepracticed. For example, Perry's Chemical Engineers' Handbook; Green. D.W.; Perry, R. H.; McGraw-Hill (2008) pg 11-90-11-93 discloses othervariations of absorptive refrigeration cycles using liquids differentthan we use, but many of those variations otherwise can be employed inthe practice of this invention.

In addition, various additives can be added to the refrigerant system ofthis invention. For example, to avoid polymerization of the olefinrefrigerant during service, stabilizers may be added. Such stabilizersare known, for example, and include terpenes, epoxides and the like.Other optional additives to add to the refrigerant include

-   -   1. antioxidants e.g., phenol based such as BHT    -   2. extreme pressure additives—chlorinated materials, phosphorous        based materials—tricresyl phosphate, sulfur based materials    -   3. antifoam additives (e.g., silicones)    -   4. oiliness additives (e.g., organic acids and esters)    -   5. acid catchers (e.g.,) epoxides

Example 4

With particular reference to the figure provided above, the efficiencyof the absorption cycle is calculated as Qcooling/(Qin+WP). Even thoughQin is considered waste heat and is a “free” source of energy this isthe best way to compare potential refrigerant pairs. A typical NH3-waterabsorption cycle operates with a COP=˜0.5-0.6 at an evaporatortemperature of 5° C. and an ambient temperature of 40° C. One absorptionrefrigeration pair according to the present invention is HFO-1234yf anda PAG oil. This particular absorption pair benefits from the fact thatthe PAG oil has a negligible vapor pressure so that the separation inthe generator becomes very simple. When operated at an evaporatortemperature of 2° C. and a ambient temperature of 40° C. the COP of thiscycle is ˜0.6 which is nearly identical to that of an ideal NH3-watersystem.

1. A method for providing refrigeration, comprising: a. evaporating afirst liquid-phase refrigerant stream comprising one or more fluorinatedorganic compounds having from one to eight carbon atoms, to produce alow-pressure vapor-phase refrigerant stream, wherein said evaporatingtransfers heat from a system to be cooled; b. contacting saidlow-pressure vapor-phase refrigerant stream with a first liquid-phasesolvent stream comprising one or more organic compounds having anaggregate number of carbon/oxygen atoms that is at least two (2) greaterthan an aggregate number of carbon/oxygen atoms in the refrigerant underconditions effective to dissolve substantially all of the refrigerant ofthe vapor-phase refrigerant stream into the solvent of the firstliquid-phase solvent stream to produce a refrigerant-solvent solutionstream; c. increasing the pressure and temperature of therefrigerant-solvent solution stream; d. thermodynamically separatingsaid refrigerant-solvent solution stream into a high-pressurevapor-phase refrigerant stream and a second liquid-phase solvent stream;e. recycling said second liquid-phase solvent stream to step (b) toproduce said first liquid-phase solvent stream; f. condensing saidhigh-pressure vapor-phase refrigerant stream to produce a second liquidphase refrigerant stream; and g. recycling said second liquid-phaserefrigerant stream to step (a) to produce said first liquid-phaserefrigerant stream.
 2. The method of claim 1 wherein said one or moreorganic compounds in said first liquid-phase solvent stream has aboiling point that is at least 40° C. higher than the boiling point ofthe one or more organic compounds in said first liquid-phase refrigerantstream.
 3. The method of claim 1 wherein one or more organic compoundsin said first liquid-phase refrigerant stream are selected from thegroup consisting of HFCs, HFOs, HFCOs, CO2, and combinations thereof. 4.The method of claim 3 wherein said one or more organic compounds in saidfirst liquid-phase refrigerant stream are selected from one or more of1,1,1,2-tetrafluoropropene, difluoromethane,trans-1,1,1,3-tetrafluoropropene, cis-1,1,1,3-tertafluoropropene,3,3,3-trifluoropropene, and combinations thereof.
 5. The method of claim1 wherein said one or more organic compounds in said first liquid-phasesolvent stream are selected from the group consisting of fluoroethers,fluoroketones, HFC, HFOs, HFCOs, and combination thereof.
 6. The methodof claim 5 wherein the organic compounds in said first liquid-phasesolvent stream are selected from the group consisting of nonafluorobutylether, perfluoro(2-methyl-3-pentanone), 1,1,1,3,3-pentafluoropropane,1-chloro-3,3,3-trifluoropropene, and combinations thereof.
 7. The methodof claim 1 wherein said one or more organic compounds in said firstliquid-phase refrigerant stream are selected from one or more of1,1,1,2-tetrafluoropropene, difluoromethane,trans-1,1,1,3-tertafluoropropene, cis-1,1,1,3-tertafluoropropene,3,3,3-trifluoropropene, and combinations thereof and said organiccompounds in said first liquid-phase solvent stream are selected fromthe group consisting of nonafluorobutyl ether,perfluoro(2-methyl-3-pentanone), 1,1,1,3,3-pentafluoropropane,1-chloro-3,3,3-trifluoropropene, and combinations thereof.
 8. The methodof claim 1 wherein said one or more organic compounds in said firstliquid-phase refrigerant stream comprises at least one compound havingthe formula C_(w)H_(x)F_(y)Cl_(z) where w is an integer from 3 to 5, xis an integer from 1 to 3, z is an integer from 0 to 1, and y=2w−x−z. 9.The method of claim 1 wherein said solvent is selected from the groupconsisting of poly-ethylene glycol oils, polyol ester oils,polypropylene glycol dimethyl ether-based and mineral oil.
 10. Themethod of claim 1 wherein said increasing the temperature of saidsolution in step (c) involves the transfer of heat from a source ofindustrial waste heat to said solution.
 11. The method of claim 1wherein said increasing the temperature of said solution in step (c)involves the transfer of geothermal heat to said solution.
 12. Themethod of claim 1 wherein said increasing the temperature of saidsolution in step (c) involves the transfer of solar heat to saidsolution.
 13. An absorption refrigeration system comprising: a. arefrigerant selected from the group consisting of one or morefluorinated organic compounds b. an absorbent comprising one or morefluorinated organic compounds having from one to eight carbon atoms(C1-C8) having a boiling point that is at least 40° C. higher than theboiling point of the refrigerant; c. an evaporator suitable forevaporating said refrigerant; d. a mixer suitable for mixing saidrefrigerant with said absorbent, wherein said mixer is fluidly connectedto said evaporator; e. an absorber suitable for dissolving at least aportion of said refrigerant into said absorbent to produce a solution,wherein said absorber is fluidly connect to said mixer; f. a pumpfluidly connected to said absorber; g. a heat exchanger fluidlyconnected to said pump; h. a separator suitable for thermodynamicallyseparating said solution into a vapor refrigerant component and a liquidabsorbent component, wherein said separator is fluidly connected to saidheat exchanger; i. an oil return line fluidly connected to saidseparator and said mixer, and j. a condenser suitable for condensingsaid vapor refrigerant component, wherein said condenser is fluidlyconnected to said separator and said evaporator.
 14. The method of claim13 wherein the refrigerant is selected from the group consisting ofHFCs, HFOs, HFCOs, CO2, and combinations thereof.
 15. The method ofclaim 14 wherein the refrigerant is selected from one or more of1,1,1,2-tetrafluoropropene, difluoromethane,trans-1,1,1,3-tertafluoropropene, cis-1,1,1,3-tertafluoropropene,3,3,3-trifluoropropene, and combinations thereof.
 16. The method ofclaim 13 wherein the absorbent is selected from the group consisting offluoroethers, fluoroketones, HFC, HFOs, HFCOs, and combination thereof.17. The method of claim 16 wherein the absorbent is selected from thegroup consisting of nonafluorobutyl ether,perfluoro(2-methyl-3-pentanone), 1,1,1,3,3-pentafluoropropane,1-chloro-3,3,3-trifluoropropene, and combinations thereof.
 18. Thesystem of claim 13 wherein said refrigerant comprises at least onecompound having the formula C_(w)H_(x)F_(y)Cl_(z) where w is an integerfrom 3 to 5, x is an integer from 0 to 3, z is an integer from 0 to 1,and y=2w−x−z, provided that x and z are not both zero.